Heretofore, there is a known method and apparatus for folding up an air bag as disclosed in Japanese Patent Publication No. Hei. 4-8647. The conventional folding method comprises the steps of, as shown in FIG. 1, folding a horizontally-spread air bag crosswise into the figure of a bellows so as to decrease its width crosswise and, as shown in FIG. 2, folding the air bag folded up lengthwise by folding it down the middle into the figure of a bellows.
Under the conventional folding method, however, such an air bag is allowed to easily jut upward in the initial stage of its inflation and in order to improve this point, it was contrived to fold an air bag lengthwise in the form of FIG. 3 (Japanese Patent Application No. Hei. 6-162360).
The profile of the air bag thus folded up crosswise and lengthwise according to the improved version above shows that left and right regions 3, 4 near the center of the air bag 2 folded up crosswise come closer to each other toward the center thereof and subsequently extend upward, whereas both the left and right end sides 5, 6 of the air bag 2 folded up crosswise are arranged outside the left and right regions 3, 4 on the center side thereof, respectively.
When the air bag is folded into the aforementioned profile by means of the folding apparatus equipped with a conventional folding bar, the folding operation is to be performed from the central regions 3, 4 of the air bag to both the left and right end sides 5, 6 in sequence. However, a great deal of tension is applied when both the left and right end sides 5, 6 are folded up, which results in holding the folding bar unmovable. Consequently, the automated operation of folding air bags still remains unfeasible.